1. Swedish National Graduate School of Space Technology Cluster multi-spacecraft measurements: applications on transition layer development and location of the reconnection site Lars-Göran Westerberg 1, Hans O. Åkerstedt 1 and Hans Nilsson 2 1 Division of Fluid Mechanics Luleå University of Technology 2 Swedish Institute of Space Physics, Kiruna

2. Swedish National Graduate School of Space Technology Outline Introduction - Objective of present paper. - The magnetosphere and Cluster spacecraft orbit. - Magnetic reconnection and the Cluster mission. Cluster in situ measurements coupled with a 3D analysis. Conclusions and future work.

3. Swedish National Graduate School of Space Technology Objective of present paper  Combine results from a 3D analysis covering the plasma flow near a reconnection site with in situ Cluster observations, in order to study: Development of the magnetopause transition layer. Values on the anomalous transport coefficients ( ν + η d ), where ν is the kinematic viscosity and η d the magnetic diffusivity. Also estimate the distance from the observing spacecraft to the reconnection site.

4. Swedish National Graduate School of Space Technology The magnetosphere and Cluster spacecraft orbit

5. Swedish National Graduate School of Space Technology Magnetic reconnection Main mechanism for the transfer of mass and momentum in space and astrophysical applications. Magnetic field seize to be frozen in the plasma. The resistivity is locally finite. Credit: European Space Agency

6. Swedish National Graduate School of Space Technology Results from 3D analysis To be coupled with data from the Cluster spacecraft* *Grammatical notation: One spacecraft, several spacecraft

7. Swedish National Graduate School of Space Technology y z x Cluster spacecrafts Magnetopause ~8 R E ~9 R E Earth Bow shock z x Magnetosheath y Sub-Solar point a b c sc1 sc4 sc3 sc1 sc4 sc3 sc1 sc4 sc3 Joint position on the 13th of January 2002 Sub-solar region

8. Swedish National Graduate School of Space Technology Cluster sc1 data during 14:50-15:50 Time (UT)

9. Swedish National Graduate School of Space Technology Results from Cluster and theory x (R E ) B (nT) V (km/s)

10. Swedish National Graduate School of Space Technology (distance to reconnection line) y z Z x U HT reconnection line Z0Z0 satellite a Z (Distance from reconnection site) b δ(Z) sc4 sc3sc1 Location of reconnection line and transition layer development Solid line: Theoretical expression. Cross marks: Measured thickness by respective spacecraft

11. Swedish National Graduate School of Space Technology Conclusions and future work  Maximum value of anomalous transport coefficients ~ 10 4 km 2 /s.  Cluster satellites pass the magnetopause ~ 0.5 R E from the reconnection site.  Magnetopause transition layer increases when moving away from the reconnection site.  Enhance the data analysis – statistical study of magnetopause crossings.  Develop the theory by including Hall terms as non- ideal effects.

12. Swedish National Graduate School of Space Technology Any questions? Ask Eddie